The present invention relates to an improved hydraulic cylinder, especially to a double-rod cylinder for an exerciser.
A conventional hydraulic cylinder for an exerciser, having a casing and a piston with a single piston rod attached, does not have working fluid filling the cylinder on the side of the piston head which has the piston rod connected. This ram-type cylinder only effectively acts in one direction.
For a conventional double-rod hydraulic cylinder, an oil tank or a reservoir is needed for the working fluid to circulate therethrough. Further to this, if an oil tank or a reservoir is not provided, the working fluid is pressurized within the cylinder and exerts a pressure on the inner walls of the cylinder. The pressure existing therein may reach up to 3000 psi, causing a large increase in temperature. Moreover, the high internal pressure experienced will cause a reduction in the durability of the hydraulic cylinder.